Bun proxy-chain library compatibility issues: Connection reset and undefined connectionId

[smmoosavi]

Description

When using the proxy-chain library with Bun, several critical issues occur that don't happen with Node.js:

1. Connection Reset: HTTP requests with chunked transfer encoding result in connection reset errors
2. Undefined connectionId for short-lived connections: The connection identifier is undefined for short-lived connections (like quick HTTPS CONNECT requests), while long-lived connections do get a connectionId but never properly close (see issue 4)
3. Connection statistics always zero: All byte counters (srcTxBytes, srcRxBytes, trgTxBytes, trgRxBytes) remain at zero despite data transfer
4. connectionClosed event never fired: The event is never called, causing long-lived connections to accumulate indefinitely in the active connections list

Reproduction

I've created a minimal reproduction repository:

Repository: https://github.com/smmoosavi/bun-proxy-chain-bug

Steps to Reproduce

1. Clone the repository
2. Run pnpm install
3. Open three terminals

Terminal 1:

node waiting-http-server.mjs

Terminal 2:

bun test-proxy.mjs | tee bun-output

Terminal 3:

export https_proxy=http://127.1:4090 http_proxy=http://127.1:4090

curl https://google.com
curl http://127.0.0.1:6000

For a clearer demonstration of connection accumulation, run the curl commands twice:

export https_proxy=http://127.1:4090 http_proxy=http://127.1:4090

curl https://google.com ; curl http://127.0.0.1:6000
# wait a few seconds
curl https://google.com ; curl http://127.0.0.1:6000

Expected Behavior (Node.js)

When running with Node.js (node test-proxy.mjs), the proxy server:

• Assigns valid connectionId values (including for CONNECT/HTTPS requests)
• Tracks byte statistics correctly (non-zero values reflecting actual data transfer)
• Completes chunked transfer responses successfully
• Fires connectionClosed events when connections are closed

The curl request completes successfully with output:

0
1
2
3

Actual Behavior (Bun)

When running with Bun (bun test-proxy.mjs), the proxy server:

• Provides undefined for connectionId in prepareRequestFunction for short-lived connections (quick HTTPS requests)
• Provides a valid connectionId for long-lived connections, but these connections never close
• Reports all connection statistics as zero (srcTxBytes, srcRxBytes, trgTxBytes, trgRxBytes all remain 0)
• Causes "Connection Reset" error on the client side for chunked responses
• Never fires connectionClosed events - long-lived connections accumulate in the active list (e.g., [0], then [0, 1], then [0, 1, 2]...)

The curl request fails with:

Connection Reset%

Additional Context

The test setup uses a simple HTTP server with chunked transfer encoding (waiting-http-server.mjs) to expose the connection handling issues. The proxy server (test-proxy.mjs) is minimal and only logs connection details without any complex logic.

Output files are included in the repository:

• node-output and bun-output - single curl run
• node-output-2 and bun-output-2 - double curl run (clearly shows connection accumulation in Bun)

According to Bun's Node.js compatibility documentation:

If a package works in Node.js but doesn't work in Bun, we consider it a bug in Bun. Please open an issue and we'll fix it.

Since proxy-chain works correctly in Node.js but fails in Bun, this qualifies as a Bun bug per their own criteria.

Environment

• Bun version: 1.3.7
• Node.js version: v22.14.0 (for comparison)
• OS: Ubuntu 24.04.3 LTS (Linux 6.14.0-37-generic x86_64 x86_64)
• proxy-chain version: ^2.7.1

[github-actions]

Found 3 possible duplicate issues:

1. proxy-chain package does not work bun #9786
2. puppeteer with proxy doesn't work #12213
3. node:http ServerResponse doesn't emit close event #14697

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